"Man on Wire," about the French daredevil who once tightroped between the World Trade Center's twin towers, is a wistful remembrance of past glory  of the man, of lower Manhattan, and of who we were in the '70s.

What charmed and delighted me most about "Man On Wire" was not the fact of Philippe Petit's walk on a wire strung between the observation decks of the Twin Towers in 1974  a gaspingly beautiful feat, but not itself a springboard for ebullience.

It was the fact that I walked out of this documentary  one with a historically sober setting (there is no direct reference to 9/11 in the film, but it's felt in every Twin-Tower capturing frame)  charmed and delighted to begin with. Indeed, James Marsh's 90-minute film  which swept Audience and Grand Jury Awards at Sundance and other festivals  is as impish and playful as Philippe Petit, its nimble, wire-walking subject. The footage of this Frenchman's famous walk, along with the re-enactment of the super-secret, eight-month lead-up to it, has the lightness and humor of an old-fashioned spy spoof, turning abruptly (and jokingly) noir during the climactic long night prior. "Man On Wire" is not a comedy, but it is entertaining to the bone  a quality that could have been overlooked under a lesser director. In this case, life and death form subtext aplenty.

Philippe Petit speaking in "Man on Wire."

After all, this movie is about a prank, albeit one that was potentially fateful (splat!) for its monkey-like conspirator. Scrape away this layer, and you have a resonant love letter to New York in its Seventies-era dirt and grime (and crime), to the then-budding Financial District, in the afterglow of its poignant new twin shadows. In a movie made by an Englishman about a Frenchman, it's an unexpectedly patriotic love letter, tempered only by gentle (and accurate) criticism of our "finger-snapping" American impatience.

For those of us who lived through them, be prepared to feel nostalgic for the Seventies. Who knew that white afros, handlebar moustaches, long hair, free sex, and bellbottoms (strange: hard hats haven't changed) would reference sweeter, more innocent times? Petit performed his feat the same week that Watergate reached its climax; Nixon resigned the following day  milestones elegantly rendered. Petit himself received a slap on the wrist for what he did  a trespassing charge and a wink from the judge.

On a deeper level, Marsh's film is about the momentum and endurance of passion. In present-day interviews, a middle-aged Petit comes across as more animation than human, more boy than man, as ready to utter "ha ha" (with emphatic French head gestures) as he is to laugh, leaving his audience chuckling in the void, even while he weighs in on the severity of his craft. "What a beautiful death," he exclaims, mime hands flying, "to die in the exercise of your passion." Of course, Petit didn't die, but you are left pondering his embrace of the possibility when he finally steps onto the wire just after sunrise, a slim shape in a black sweater and dark bellbottoms, the balancing pole twice as long as he is tall.

The glory belongs to Petit's co-conspirators, too  zany and (mostly) loyal characters such as Barry Greenhouse ("the inside man"), Annie Allix, his girlfriend, and Jean-Louis Blondeau, a childhood friend. The walk is every bit as much their achievement as it is Petit's  sans fame, or looming death.

For me, the real tragedy behind Petit's story was that it marked the end of a promising clandestine career. Thirty-four years afterward, one gets the distinct sense that the World Trade Center achievement, preceded by stunts at Notre Dame Cathedral and the Sydney Harbour Bridge, remains the climax of Petit's life. The press notes that accompany the film contain a list of his post-1974 performances  events with fanfare, rife with ribbon cuttings and global broadcasts, choreography and operatic soundtracks. Edgy prankster becomes overnight circus sensation whose acts suddenly bear little resemblance to his illegal walk into a hazy sunrise. Was this a result Petit would have wanted in his 20s? His eyes sparkle when he recalls the past, and he doesn't say anything about the present.